Asteroid Re-Direct: Finding a Candidate

by Paul Gilster on February 17, 2014

It was just a year ago, on February 15, 2013, that the 30-meter asteroid 2012 DA14 whisked past the Earth at a distance of well less than 30,000 kilometers, inside the orbits of our geosynchronous satellites. If you don’t recall 2012 DA14, it’s probably because it was later on the same day that the Chelyabinsk impactor struck, a 20-meter asteroid that released the energy of approximately 460 kilotons of TNT. Chelyabinsk made it into 2014 Olympic news at Sochi, with ten gold medals for February 15 winners being embedded with fragments from the object.

Today we get the passage of near-Earth asteroid 2000 EM26, whose closest approach will be covered by the Slooh network of automated telescopes starting at 2100 EST (0200 UTC), live from the Canary Islands. An iPad app is available or you can watch on Slooh.com, with the live image stream accompanied by commentary from astronomer Bob Berman and guests discussing the event and fielding questions from viewers using the hashtag #asteroid. Berman notes the significance of asteroid tracking and developing future mitigation strategies:

“On a practical level, a previously-unknown, undiscovered asteroid seems to hit our planet and cause damage or injury once a century or so, as we witnessed on June 20, 1908, and February 15, 2013. Every few centuries, an even more massive asteroid strikes us — fortunately usually impacting in an ocean or wasteland such an Antarctica. But the ongoing threat, and the fact that biosphere-altering events remain a real if small annual possibility, suggests that discovering and tracking all NEOs, as well as setting up contingency plans for deflecting them on short notice should the need arise, would be a wise use of resources.”

The Challenge of Asteroid Capture

With almost 11,000 near-Earth objects now discovered, the astronomical community continues its work on planetary defense. The Asteroid Redirect Mission (ARM) is NASA’s bid to find a small asteroid that can be parked in a lunar orbit for study and thorough exploration in the 2020s. This JPL news release gives us more information about ARM’s current status, noting two possible scenarios: An entire small asteroid could be captured and redirected into lunar orbit, or a large boulder or other mass from a larger asteroid could be retrieved and put into a similar orbit.

Image: This concept image shows an astronaut preparing to take samples from the captured asteroid after it has been relocated to a stable orbit in the Earth-moon system. Hundreds of rings are affixed to the asteroid capture bag, helping the astronaut carefully navigate the surface. Credit: NASA/JPL.

But finding the right asteroid is tricky business. Most near-Earth asteroids are either too large or in unsuitable orbits, and would-be targets can move out of range of our instruments so fast that it becomes a challenge to get enough data to make the call. The goal is something smaller than about twelve meters across, says Paul Chodas, a senior scientist in the Near-Earth Object Program Office at JPL. He adds: “There are hundreds of millions of objects out there in this size range, but they are small and don’t reflect a lot of sunlight, so they can be hard to spot. The best time to discover them is when they are brightest, when they are close to Earth.”

The news release goes through the detection and analysis process. The coordinates of objects detected by asteroid surveys flow to the Minor Planet Center in Cambridge, MA, where the objects can be tagged as previously known or else given a new designation. Orbit, intrinsic brightness and other data are then refined by the Near-Earth Object Program Office at JPL, which updates its online small body database. Now in place for the projected asteroid redirect mission is a new screening process that scans for candidate objects.

Radar observations by the Deep Space Network at Goldstone (CA) or Arecibo Observatory in Puerto Rico can produce further data on orbit and size if they are able to track the asteroid, but other observatories both professional and amateur may also be asked to look at it. The Infrared Telescope Facility at Mauna Kea can provide details on spectral type, reflectivity and likely composition. Several dozen 6- to 12-meter asteroids are thought to fly by the Earth at a distance closer than the Moon every year, but few of these are in suitable orbits for the ARM mission.

Even so, the wave of new technology now approaching should make finding the right object a sure thing. Lindley Johnson (Near-Earth Objects Program, NASA headquarters) notes what we can expect:

“The NASA-funded Catalina Sky Survey, which has made the majority of NEO discoveries since its inception in 2004, is getting an upgrade. We also will have new telescopes with an upgraded detection capability, like PanSTARRS 2 and ATLAS, coming online soon, and the Defense Advanced Research Projects Agency’s new Space Surveillance Telescope will give us a hand as well.”

And don’t forget our old friend WISE, which I usually write about in terms of brown dwarfs in the Sun’s vicinity. The repurposed spacecraft now functions as NEOWISE and may help in characterizing targets for the redirect mission.

Potential candidates are being flagged at the rate of about two per year, a number that is bound to climb as these further resources come into play. We’ll then have a target and a plan as we proceed in our efforts to characterize these objects. NASA is assuming that an Orion spacecraft and Space Launch System (SLS) rocket will make asteroid capture happen, but whatever the hardware, studying small asteroids up close — and ultimately developing strategies for nudging the trajectories of much larger objects — is a vital part of future planetary defense.

Most near-Earth asteroids are either too large or in unsuitable orbits, and would-be targets can move out of range of our instruments so fast that it becomes a challenge to get enough data to make the call. The goal is something smaller than about twelve meters across (…)

This reminds me of a Peanuts cartoon. Linus is telling Lucy that he can swim. But only 4 feet. If he is ever on a sinking ship, and if it is only 4 feet from shore, he won’t have a thing to worry about.

Nasa’s original mission was to rendezvous with an asteroid in deep space. (See the talk by Robert Landis at SETI). This would have broken new ground with flight hardware as a precursor to a Mars mission. This presumably proved too difficult (risky), so the plan changed to a safer one, capturing a small asteroid for rendezvous in cis-lunar space. Astronauts taking samples fit nicely into the sexy narrative of private asteroid mining companies harvesting the wealth of the asteroids. However retrieving little rocks adds very little to the technologies that we need for diverting big rocks for planetary defense, or the robotic technologies needed for asteroid mining, or the partial recycling life support systems for deep space crewed missions.

As we’ve seen repeatedly with disasters that happened, or potentially will happen, on Earth, legislators will kick the can down the road for projects dealing with large impact, low probability events, due to short term thinking, but will mobilize some help after a disaster strikes, even though the aggregate costs to the victims far exceeds any support they receive. Those may be the political realities, but, IMO, they do not bode well, even if a NEO survey found a high probability large impactor that would hit in just a few decades.

Interesting.
Though, I wonder if this NASA program is disabling private ventures that were attempting to assess asteroids for possible exploitation, such as Deep Space Industries and Planetary Resources. Their 2-5 year plans for assessment and capture have interestingly disappeared from their websites over the last several months. An article in The Economist recently discusses lunar property rights and suggests that control, for exploitation purposes, of heavenly bodies is still very much up for grabs, despite previous international agreements. Though, I certainly welcome ARM for its duties to humanity in an emergency capacity.

Fascinating stuff! Although I have doubts whether this mission will ever see the light of day. Seriously, what will it be this time – a 15 year wait for a mission to a boulder/rubble pile in cislunar space? How wonderful! Then what? Another 20 year wait for a Mars flyby? Perhaps a better bet for the future for manned spaceflight lies in private industry working with NASA. Yes, even though I realize that it is likely much overhyped, I’m talking SpaceX.

It’s more convenient to just go to Chelyabinsk in Central Russia. They have half a ton large fragments of a 20 meter diameter meteorite. Much larger than the meteoroid that NASA has proposed to tow to Lunar orbit.

Personally, I think that space flight should instead be used for stuff which cannot be achieved with a cheap bus drive.

“Their 2-5 year plans for assessment and capture have interestingly disappeared from their websites over the last several months. ”

That has nothing to do with anything NASA has done. NASA’s current asteroid capture program is completely and utterly in the concept stage — it’s years away from getting funding, never mind from actually accomplishing anything.

If the private asteroid companies have quietly backed off from their initial public announcements… well, there are various possible explanations. “Their initial public announcements were optimistic vaporware designed to attract investors rather than sincere, well-grounded plans of action” would be my personal choice, but YMMV.

The detection of all possible NEO impactors is a work well in progress. It’s already complete for civilization-killing asteroids, and will be complete for everything down into the tens-of-kilotons range sometime in the 2030s.

People don’t really grasp how few NEOs there actually are, nor how good our telescopes and search programs have gotten. We already know, to a high degree of certainty, that no large (>300m) asteroid is going to hit us in the next couple of hundred years. By the end of the next decade we’ll have that down to 100m, and well before midcentury we’ll have most of the Chelyabinsk-size impactors mapped as well. At that point the game will be pretty much over; anything that could do serious damage, we’ll see coming years to decades in advance.

Whenever I point this out on a space-related forum, I get pushback, because a lot of people are psychologically invested in The Asteroid Threat. But it never was actually that much of a threat, and it’s rapidly disappearing.

Jer: That’s my suspicion: Nasa doesn’t really expect to do this, ever. They’re just proposing to do it, to spike the private companies that were upstaging them. Who’s going to pay those companies to do something NASA might do for “free”?

Planetary Resources was embarrassing them, and something had to be “done” about it. But everybody who’s been paying attention to NASA knows this mission will never fly.

@Eric: Your comment and skepticism are widely shared among space enthusiasts, I fear, and for very good reasons. NASA as she stands is a rudderless hulk. An interesting piece recently in Slate asked ‘What is NASA For?”; there is a very long comment thread at NASAWatch worth reading as the thread is populated by many NASA folks.

In fairness, NASA has a huge elephant or two strapped to the back. The SLS is one; there are no missions for that bird, cool as it is, yet our Senate will have the rocket…err, jobs.

These are not good days for our beloved institution, wracked by political porkitude.

A decadal survey for human scientific exploration of space: a focus on discovery

Winning broad support for human space exploration efforts, be they to the Moon, asteroids, or Mars, has long been challenging. Matt Greenhouse argues its time for human spaceflight at NASA to adopt the approach for choosing missions that has generated considerable success for the agency’s science programs.

Four years ago, NASA set aside plans for a human return to the Moon in the foreseeable future in favor of expeditions to asteroids and Mars. In the first of a two-part article, Anthony Young reexamines the potential scientific, geopolitical, and commercial benefits of reconsidering human lunar exploration.

In the second part of his examination of the future of lunar exploration, Anthony Young looks at a new NASA initiative to support commercial robotic lunar landers and the role it could play in stimulating later human missions back to the Moon.

We already know, to a high degree of certainty, that no large (>300m) asteroid is going to hit us in the next couple of hundred years. By the end of the next decade we’ll have that down to 100m, and well before midcentury we’ll have most of the Chelyabinsk-size impactors mapped as well.

Things have moved fast. Less than a decade ago, I went to a lecture by Morrison and the message was very different. If an asteroid was on a collision with Earth, coming in on a highly elliptical orbit, wouldn’t it be undetected until it was almost on top of us? Even f it was detected out as far as Jupiter, we wouldn’t have much time to act to deflect it, assuming we had the capability.

“If an asteroid was on a collision with Earth, coming in on a highly elliptical orbit, wouldn’t it be undetected until it was almost on top of us? ”

1) Very few NEOs have highly elliptical orbits. Very, very few.

2) Even if the orbit is quite elliptical, sooner or later the NEO is going to pass within an AU or less from Earth. That means it’s very likely to get picked up by Earth-based telescopes. If something is more than 500m across, and is not unusually dark, and passes within less than an AU from Earth, either it’s already been found or it’s almost certainly going to be found in the next few years.

I don’t know who Morrison is, but I’ll note that there’s a cottage industry within the space community hyping the Asteroid Menace. This was barely acceptable ten years ago; it’s nonsense on stilts today, and nobody who is pushing it should be taken seriously. If you encounter someone who wants you to be alarmed about asteroid impacts, ask him or her politely how the asteroid manages to avoid being detected, and the impact predicted, many years (most likely decades) in advance.

Are you arguing that once we have detected all possible large impactors, that we will know in advance when we will be hit, rather than a surprise? If so, does that mean we should wait for all asteroids of damaging size be mapped before we spend considerable resources on planetary defense, because we may not need to for decades?

“Though, I wonder if this NASA program is disabling private ventures that were attempting to assess asteroids for possible exploitation, such as Deep Space Industries and Planetary Resources. ”

Just the opposite, I believe. The asteroid redirect vehicle would be a robust SEP vehicle based on the one described in the Keck Institute’s Asteroid Feasibility Study. Authors of this study include Chris Lewicki, John S. Lewis and other prominent asteroid advocates. Many of these people are in Planetary Resources and Deep Space Industries.

The report estimates the vehicle would cost 2.6 billion. $1.3 billion would be in development costs.

The odds are good that Planetary Resources will be able to accomplish the first step of their plan: Building a fleet of prospector probes, the Arkyds. But developing a nearly $3 billion retrieval vehicle? That’s a long shot.

I expect Planetary Resources would be delighted if NASA financed R&D that makes such a vehicle possible

“The detection of all possible NEO impactors is a work well in progress. It’s already complete for civilization-killing asteroids, and will be complete for everything down into the tens-of-kilotons range sometime in the 2030s. ”

I would agree we have a complete inventory of Chicxulub sized rocks.

But the Tunguska and Chelyabinsk sized rocks? Not even remotely so. And I don’t see any guarantee that we would have a complete inventory by 2030.

And what if we find a Tunguska sized rock with our name on it a decade before impact? What do we do? At this point all we could do is evacuate the impact region. Knowing about an impactor and being able to move it are two different things.

“It’s more convenient to just go to Chelyabinsk in Central Russia. They have half a ton large fragments of a 20 meter diameter meteorite. Much larger than the meteoroid that NASA has proposed to tow to Lunar orbit.”

The resource Planetary Resources hopes to mine first is water.

To reach destinations in space we have a minimum delta V budget of 9 km/s to reach low earth orbit. This combined with the rocket equation makes economic space flight very hard. Presently the only practical way to meet the extremely difficult mass fractions is by using multi-stage expendables.

Propellent high on the slopes of earth’s gravity well would break the exponent in Tsiolkovsky’s rocket equation. With small delta V budgets, single stage reusable vehicles become doable.

Possible sources of extraterrestrial propellent are near earth asteroids and the permanently shadowed regions of the moon. Proponents of extra-terrestrial propellent include Jeff Greason, Planetary Resources, Paul Spudis, astronaut Don Pettit and others.

Yes, there is plenty of water on earth. But it is 9 km/s from LEO. Propellent at the bottom of a deep gravity well does nothing to break the exponent in the rocket equation.

@Hop David
In general, water must be rare inside the frost line which through the asteroid belt. Some eccentric astroids may have it, though. But to find them, one must examine MANY of them, not towing yet one of those tiny ones to Lunar orbit, of the type which we already have a great collection of as old and new meteorites on Earth. The Chelyabinsk event gave us more for free than the NASA meteoroid re-direct mission could delivier at a multi-billion price tag 10 years from now.

Maybe NASA should “retrieve” the fragments of the Chelyabinsk meteoroid to a lunar orbit in space :-D That would be much cheaper and could be done already this year. And the result would be the same, a meteoroid in Lunar orbit, and as pointless scientifically, mining economically, technologically and for purposes of planetary defence. The asteroid retrieval mission is a PARODY of space flight, I hope and predict that it will never happen.

@Doug M.
I agree that the asteroid threat seems to be well under way to be handled by discovery of objects and their orbits. But then there’s the COMET threat…

@Glaas There are plenty of carbonaceous near earth asteroids with hydrated clays.

“Maybe NASA should “retrieve” the fragments of the Chelyabinsk meteoroid to a lunar orbit in space”

Sigh. I’m guessing I’m wasting my breath since it flew over your head the first time. But here goes: these fragments are 9 km/s from LEO. 13 km/s from a lunar orbit. They do nothing to break the exponent in the rocket equation.

On the other hand there are carbonaceous asteroids that could be parked in lunar orbit for around .2 km/s

It may be small by cosmic standards, but it could still cause damage and injuries to a populated area if it ever struck Earth. As for the Tunguska Event of 1908, it is nothing short of a miracle it did not come down on a city.

“As for the Tunguska Event of 1908, it is nothing short of a miracle it did not come down on a city.”

Since cities in 1908 occupied less than one tenth of one percent of the Earth’s surface, it was a fairly likely miracle.

78% water, and about a third of the land is either desert, tundra or ice cap. The odds of a random megaton or less impactor hitting something significant are actually rather low. The most amazing thing about Chelyabinsk is that it hit near Chelyabinsk, as opposed to the Pacific, the Antarctic, or the Sahara.

@Hop David
The astronauts in the Orion would be much more expensive to launch with the SLS, to examine the meteoroid once in lunar orbit, than launching the Chelyabinsk fragment with an Atlas rocket. The Chelyabinsk fragment could be thoroughly examined here on Earth before launch. If the purpose is just to give the Moon a moon…

The asteroid idea was from the beginning to actually travel to a real asteroid of 100+ meters. This retrieval circus is a parody on space exploration.

Doug M said “ comet impacts on earth seem to be very very rare, at least in the last few hundred million years.” and from what I can tell that is based on their observed frequencies not from analysing impacts.

I can’t help noticing Shoemaker-Levy 9 broke up into about twenty large fragments. Had its orbit been different they could have been thrown into the inner solar system increasing the chance that they would hit Earth twenty fold.

And if my uncle had, etc. First, there are a lot more comets with perihelions inside Jupiter’s orbit than there are with perihelions inside Earth’s orbit. Second, Jupiter is over 300 times more massive than Earth, which makes it a much more probable target. If Earth had been in Jupiter’s place, Shoemaker-Levy would never have come near it! The only reason it was there in the first place is because Jupiter’s gravity had already captured it twice, once as a short-period comet, and then a second time into an eccentric and unstable orbit around Jupiter itself.

The earlier statement about comet impacts on Earth is indeed based on analyzing impacts. We’ve been looking for comet impact traces on Earth for a while now. Oddly, that search has not turned up much.

A comet impact should look rather different from an asteroid impact. A comet would be hitting a lot faster, so the pattern of energy release, fractures, melting, breccias, etc., should be noticeably different. The existence, distribution, and chemical composition of remnants (fragments and “iridium layer” type stuff) should also be different. However, we don’t know for sure, because we have yet to discover a single unambiguous comet impact signature! There are several “maybes” — the most recent being a proposed impact in Oligocene Egypt, ~28 million years ago, just proposed in a paper last year — but not a single “oh yeah”.

So while it’s certainly theoretically possible that a comet could hit the Earth, as far as we can tell right now it seems to have been very very rare in the past. As in, so rare we’re not yet sure whether there’s been even a single major one in the Phanerozoic (last ~half billion years).

‘First, there are a lot more comets with perihelions inside Jupiter’s orbit than there are with perihelions inside Earth’s orbit.’

Makes sense as there is lot less evaporational heat at Jupiter and Jupiter’s orbit contains a lot more space.

‘Second, Jupiter is over 300 times more massive than Earth, which makes it a much more probable target. ‘

It is also likely to bend the orbit after all it is 300 time more massive but only 120 time the area of the earth making an impact like less likely.

‘The earlier statement about comet impacts on Earth is indeed based on analyzing impacts. We’ve been looking for comet impact traces on Earth for a while now. Oddly, that search has not turned up much…’

Comets contain mostly volatile components such as water which would not make a huge signature, except maybe a D/H change, which could possibly be detected when it refroze at the poles.

‘So while it’s certainly theoretically possible that a comet could hit the Earth, as far as we can tell right now it seems to have been very very rare in the past. As in, so rare we’re not yet sure whether there’s been even a single major one in the Phanerozoic (last ~half billion years).’

Probability wise it would indicate we have been hit in the past and will continue to be hit in the future.

Solar Systems, including ours, are thought to begin as massive clouds of dust and gas surrounding young stars; over billions of years, planets form from repeated impacts of rocky debris. Asteroids and comets are left-over chunks of debris from that process which didn’t coalesce together. Such debris clouds, or protoplanetary disks, have been found around many young stars.

These are Solar Systems still in their infancy. Now, astronomers have been able to observe the actual collision between two large rocky bodies, most likely asteroids, in a protoplanetary disk surrounding a young Sun-like star 1,200 light-years away.

The impact was apparently seen by the Spitzer Space Telescope as it observed the star NGC 2547-ID8, which is about 35 million years old in the constellation Vela. A large surge of “fresh” dust was observed between August 2012 and January 2013, thought to be the result of a collision between two rocky bodies such as asteroids.

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last seven years, this site has coordinated its efforts with the Tau Zero Foundation, and now serves as the Foundation's news forum. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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